The present invention relates generally to a lapping or grinder machine and a head device manufacturing method, and more particularly to a lapping machine that equalizes the height of a head block (also referred to as a “row bar”) in which plural head devices are connected in row, and a method that grinds or polishes the head block and manufactures the head device. The present invention is suitable, for example, for a lapping machine for a head device in a hard disc drive (“HDD”).
Along with the recent spread of the Internet etc., inexpensive hard disc drives that can record a large amount of information including images have been increasingly demanded. When the surface recording density is increased to meet the demand for the large capacity, a minimum unit of the magnetic recording information or a 1-bit area reduces on the recording medium, weakening a signal magnetic field obtained from the recording medium. A small and highly sensitive read head is necessary to read the weak signal magnetic field. A high-quality polishing process that makes constant the height of the head block is necessary for the highly sensitive read head. In addition, an expensive magnetic disc drive needs an improved yield of the lapping process and an improved economic efficiency of the lapping machine.
The head block is a workpiece made by cutting many magnetic heads formed on a wafer in a strip or bar shape. Since the head block is too thin to be directly attached to the lapping machine, it is first attached to a jig before attached to the lapping machine. The working amount of the head block is controlled through an electrical lapping guide (“ELG”) device or a resistance lapping guide (“RLG”) sensor that is attached to the head block and detects a working amount as resistance.
This assignee has proposed a lapping machine in Japanese Patent Application, Publication No. (“JP”) 2005-007571, as shown in FIG. 10. A head block 10 adhered to a bottom surface of a jig 20 contacts a grinding plane 2a of a lapping board 2. The jig 20 and the head block 10 extend perpendicularly to the paper plane shown in FIG. 10. The jig 20 has a perforation hole 21, and is attached to the back of a lapping machine body 30. A link pressure mechanism 40 is provided on a side surface 20a of the jig 20. The link pressure mechanism 40 has a power point P1, a fulcrum P2 as a rotating center, and an action point P3 that gives a perpendicular power to the jig 20 in the hole 21. For example, when the power point P1 displaces to the right in FIG. 10, the action point P3 displaces down, and the force that compresses the head block 10 against the grinding plane 2a increases. On the other hand, when the power point P1 displaces to the left, the action point P3 displaces up, and the force that compresses the head block 10 against the grinding plane 2a decreases.
The pressure by the pressure mechanism 40 concentrating only on the head block 10 would damage each head device and lower the yield. Therefore, JP 2005-1311727 proposes a dummy block that shares the load applied to the head block 10 as shown in FIGS. 11 and 12. In FIG. 11, a transfer tool 22 is attached to the back of a lapping machine body 30A, the head block 10 is adhered to a bottom surface of a jig 20A, and a dummy block 12 is adhered to a bottom surface of a jig 24. A keeper 26 connects jigs 20A and 24 to each other. The transfer tool 22 supports the jig 20A, and has a signal line that transmits an output from the RLG sensor to a controller. In FIG. 12, another jig 28 is provided on a bottom surface of the keeper 26, and another dummy block 14 is adhered onto it. The dummy block 14 is provided between the head block 10 and the dummy block 12; there are two dummy blocks 12 and 14.
According to the structure shown in FIG. 10, the lapping machine 30 directly pressures the jig 20 that supports the head block 10 using the pressure mechanism 40, while according to the structure shown in FIG. 11, the lapping machine 30A pressures the jig 20A that supports the head block 10 via the transfer tool 22. When the jig 20A inclines on the attachment surface 22a due to the error at which the jig 20A is attached to the transfer tool 22, the pressure applied by the transfer tool 22 is not uniform among the magnetic head devices in the head block 10, lowering the yield.
In addition, a connection between the transfer tool 22 and the RLG sensor is arduous, and this inventor has studied a configuration that fixes a printed board onto the side surface 20b of the jig 20 in FIG. 10 and an output of an ELG device is received via wires. In that case, the jig 20 shown in FIG. 10 serves as both the jig 20A and the transfer tool 22 in FIG. 11. In addition, this inventor has studied the configuration shown in FIGS. 11 and 12, which connects the dummy block 12 or the dummy blocks 12 and 14 to the side surface 20b via the keeper 26 and the jig 24. However, this inventor has discovered that the configuration that arranges, as shown in FIG. 11 or 12, the dummy blocks 12 and 14 on the jig 20 shown in FIG. 10 causes problems of a difficult manufacture of the lapping machine, a lowered yield of the polished magnetic head device, and a large size of the lapping machine.
In other words, it is difficult to connect the keeper 26 to the side surface 20b since the side surface 20b is mounted with the printed board and wire connections. In addition, the structures shown in FIGS. 11 and 12 requires that the bottom surface of the head block 10 and the bottom surfaces of the dummy blocks 12 and 14 be coplanar, but the coplanarity is difficult due to the processing and attachment accuracies of the jigs 20A, 24, and 28. Without the coplanarity, the load sharing functions of the dummy blocks 12 and 14 deteriorate. Moreover, the long keeper 26 increases a distance between the head block 10 and the dummy block 12, introducing diamonds and lap dusts included in the slurry between them, and causing damages of the tunneling magnetoresistive (“TuMR”) device and short circuit in the head block 10. On the other hand, use of fine diamonds may reduce damages of the head block 10, but fine diamond is expensive. In addition, the keeper 26 and the jig 24 preclude a miniaturization of the apparatus.